Equatorially mounted astronomical telescopes of the type in general use in observatories have several disadvantages. Firstly, because equatorial mountings permit the telescope to be pivoted about two mutually perpendicular axes, it is necessary that the roof of the observatory building be specially constructed to enable the telescope to be directed at various points in the sky. Typically, the roof is a rotatable, slotted dome supported by massive bearings and requiring a powerful motor drive system for its operation. Secondly, because the interior of the observatory building is open to the outside through the roof, the motor drive system and bearings for tracking are unprotected from the weather. Thirdly, telescope mountings of this type do not provide the rigidity required for certain types of observations, such as viewing the corona of the sun through a telescope of the type which artificially eclipses an image of the sun. Fourthly, in spite of the high cost of construction, observatories of this type do not provide comfortable viewing. The interior of the observatory building can neither be suitably heated nor cooled relative to the outside temperature because the resulting passage of air through openings in the roof affects viewing quality. Moreover, because the telescope proper must be moved to different positions to enable observation of different points in the sky, the eyepiece end of the telescope may assume positions in which the posture of the observer is awkward and fatiguing.